Connecticut State Police walk near the scene of an elementary school shooting on Dec. 14, 2012 in Newtown, Conn. (credit: Douglas Healey/Getty Images)

NEWTOWN, Conn. (CBS Connecticut/AP) — CBS News is reporting that at least 27 people are dead, including 20 students, after a mass shooting at the Sandy Hook Elementary School in Newtown. The gunman is among the dead.

CBS News reports the gunman, now identified as 20-year-old Adam Lanza, was the son of Nancy Lanza, a female teacher at the school. She was found dead at her Newtown home. A law enforcement officer originally told CBS News that Nancy Lanza was among the dead at the school.

New Jersey State Police have Lanza’s older brother, 24-year-old Ryan, in custody in Hoboken. WCBS-TV reports that Ryan Lanza is being cooperative with authorities and that he hasn’t been in contact with his brother for a few years.

A law enforcement official told The Associated Press that Adam Lanza’s girlfriend and another friend were now missing in New Jersey.

Lanza opened fire with two handguns inside two classrooms, one of the classrooms being his mother’s. CBS News reports that Lanza killed himself at the school.

The Associated Press quoted an official as saying the suspected gunman drove to the school in his mother’s car. Another law enforcement source earlier told CBS News that a Sig Sauer, a Glock 9 and a Bushmaster rifle were found at the scene. The AP reports that the three weapons found at the scene were registered to his slain mother.

“The shooter is deceased inside the building,” State Police Lt. Paul Vance said during a press conference on Friday afternoon, adding that the scene had been secured.

In a press conference Saturday morning, officials confirmed that Lanza forced his way into the school and that he was “not voluntarily let into the school at all,” according to the AP. Newtown police detectives also added that they could be working at the scene for another two days. Police said investigators at both the school and suspect’s home produced “good evidence” that could possibly help figure out the motive behind the heinous massacre.

Vance said that 18 children were pronounced dead at the scene and two more children died at the hospital. Six adults also were killed. The school’s principal, Dawn Hochsprung, was among the dead.

The gunman was believed to have suffered from a personality disorder and lived with his mother in Connecticut. The New York Times reports that Lanza suffered from Asperger’s syndrome, a high-functioning form of autism.

CBS News reports that a potential second suspect was in custody and that SWAT was investigating the home of the suspect. It was not known if that alleged second suspect fired any of the shots in the massacre.

A witness tells WFSB-TV that a second man was taken out of the woods in handcuffs wearing a black jacket and camouflage pants and telling parents on the scene, “I did not do it.”

NPR reported Connecticut will reach out to other states for help with autopsies because they don’t have enough medical examiners.

Two students and a teacher injured in the shooting andwere taken to Dansbury Hospital, spokeswoman Diane Burke told WCBS-TV.

In the wake of the shooting, parents flooded to Sandy Hook Elementary School, about 60 miles northeast of New York City, looking for their children. Students were told to close their eyes by police as they were led from the building.

“It was a very orderly evacuation given the circumstances,” Connecticut Post reporter Brian Koonz told WCBS-TV.

One mother told WCBS-TV reporter Lou Young that it was like a “war zone” in Newtown. Her child told Young he was about to deliver the attendance sheet to the principal’s office when bullets started flying by his head and that a teacher pulled him into a classroom.

Another mother described the devastation parents felt when they found out their children didn’t survive the shooting.

“All these parents were waiting for their children to come out, she told Young. “There were 20 parents that were just told that their children were dead.”

Police responded to the school shooting at 9:41 a.m. in what WFSB-TV reporter Len Besthoff called a “chaotic scene.”

Stephen Delgiadice said his 8-year-old daughter heard two big bangs and teachers told her to get in a corner. His daughter was fine.

“It’s alarming, especially in Newtown, Connecticut, which we always thought was the safest place in America,” he said.

Mergim Bajraliu, 17, heard the gunshots echo from his home and raced to check on his 9-year-old sister at the school. He said his sister, who was fine, heard a scream come over the intercom at one point. He said teachers were shaking and crying as they came out of the building.

“Everyone was just traumatized,” he said.

Richard Wilford’s 7-year-old son, Richie, is in the second grade at the school. His son told him that he heard a noise that “sounded like what he described as cans falling.”

The boy told him a teacher went out to check on the noise, came back in, locked the door and had the kids huddle up in the corner until police arrived.

“There’s no words,” Wilford said. “It’s sheer terror, a sense of imminent danger, to get to your child and be there to protect him.”

Melissa Makris, 43, said her 10-year-old son, Philip, was in the school gym.

“He said he heard a lot of loud noises and then screaming,” said Makris. “Then the gym teachers immediately gathered the children in a corner and kept them safe in a corner.”

The fourth-grader told his mother that the students stayed huddled until police came in the gym. He also told her that he saw what looked like a body under a blanket as he fled the school.

“He said the policeman came in and helped them get out of the building and told them to run,” Makris said. “And they ran to the firehouse.”

The school superintendent’s office says the district has locked down schools as a preventive measure to ensure the safety of students and staff. Schools in neighboring towns also were locked down as a precaution.

At the White House, a tearful President Barack Obama said he grieved about the massacre as a father first, declaring “our hearts are broken today.” He promised action to prevent such tragedies again but did not say what that would be.

The scene in the White House briefing room was one of the most outwardly emotional moments of Obama’s presidency.

“The majority of those who died were children — beautiful, little kids between the ages of 5 and 10 years old,” Obama said.

He paused for several seconds to keep his composure as he teared up and wiped an eye. Nearby, two aides cried and held hands as they listened to Obama.

“They had their entire lives ahead of them — birthdays, graduations, wedding, kids of their own,” Obama continued about the victims. “Among the fallen were also teachers, men and women who devoted their lives to helping our children.”

Connecticut Gov. Dannel P. Malloy says he’s spoken with federal officials who have offered to provide help to the state and the Newtown community in the aftermath of a deadly grade school shooting.

Malloy arrived in Newtown on Friday afternoon, hours after a shooting that left the gunman dead and at least one teacher wounded.

The governor’s office said several state agencies, including emergency management, public health and the Department of Children and Families, will be coordinating the state’s response.

In addition, Malloy says State Police are coordinating law enforcement work with federal and local authorities.

Malloy called it “a tragedy of unspeakable terms.”

This shooting rivals the massacres at Virginia Tech in 2007 where 32 people were killed and at Columbine High School in 1999 where 13 were gunned down.

The worst mass school murder in American history took place on May 18,1927 in Bath Township, Mich., when a former school board member set off three bombs that killed 45 people.